“”[Astrologers will tell you] things like: "Science doesn't know everything." Well, of course science doesn't know everything. But because science doesn't know everything, that doesn't mean science knows nothing. Science knows enough for us to be watched by a few million people now on television, for these lights to be working, for quite extraordinary miracles to have taken place in terms of the harnessing of the physical world and our dim approaches towards understanding it.

"Science doesn't know everything" (also "Science can't explain X[2]") is an argument that asserts that, because of science's lack of knowledge about something, something else must be true. The implication is that, because science does not have an answer (or a sufficiently good answer) already, any claim can take its place, even though it has no supporting evidence. The argument is closely linked to the Science was wrong before and God of the gaps arguments.

Hundreds of years ago we didn’t know radio waves existed, but they obviously did exist, so how do you know "qi" (or whatever woo idea they are promoting) does not exist today?

The answer is that we don't know. But "how do you know 'qi' does not exist?" is the wrong question. The right question is, "Is there any evidence for 'qi'?" The lack of a scientific answer does not imply that the alternate answer is more true.

It is true that something untestable is outside of science, because the scientific method relies on testing. This is a favorite of psychics and others with supposed paranormal abilities, because if their abilities don't work when they're being tested, then they can claim that their "abilities" don't work "on demand" — meaning that they operate based on some mysterious, untestable principle. However, if something is truly untestable, then this means that it follows no rules. It can happen at any time, to anyone, anywhere, for any reason, with any effect. And if something is as random as that, then it's probably not even possible to know about it. And, ultimately, just because science can't disprove something doesn't mean that it's true.

Some theists think that if science can't explain something, it follows that God is the explanation.

Often they're looking to force you to admit that science doesn't know everything, and from there admit that God could exist, with heavy implications that (their) God does exist. Alternatively, they may be an IDiot, and the next step in their "logic" is "therefore science doesn't know anything." It's a form of Moving the goalposts, in this case moving them to the absolute farthest place possible.

The argument often follows the form:

P1: Science doesn't know X.P2: Anything science doesn't know it will never know.C1: Science will never know X.C2:God did it.

The first step presumes that science has already explained everything that it is capable of explaining, which is patently false. This matches up with the other common rhetorical phrase "science doesn't know everything", which Dara Ó Briain pointed out is not a problem because science's job is to find answers, not have them all already: if it did have all the answers to everything, science would come to an end, because science is a process for exploring the world, not a bare catalog of facts. The phrase is also frequently based on misrepresenting the current state of knowledge in a particular field when in fact science does provide a satisfactory explanation. Lies of this nature, like those advanced by the creationist RATE Project, may be predicated on misapplying legitimate scientific protocols in light of known limitations, grossly misrepresenting the nature and significance of margins of error, or simply shoddy scholarship and materials handling.

The second and third points are blatant non sequiturs. Assuming that science will never have an explanation for a phenomenon is, at best, naive.

Of course it is entirely possible that there are things which science will not have worked out before the human species becomes extinct or before the end of the universe. But even in such cases that would not justify a conclusion "Therefore [the locally popular] God did it."

Typical examples of "X" in this case are the origin of life and the origin of the universe. They also include the constancy of physical constants, such as the speed of light and the decay rates of radioactive nuclei, over long or short periods of time. Issues of origins and the constancy and source of physical constants over time are key points in understanding the world around us and are currently cutting-edge biology and physics. Science, being at once descriptive, predictive, and adaptive to changing data and theories, can only get closer to an answer—whereas dismissing science is likely to get us away from an accuarte one.

Since creationists and apologists are not too big on science, they sometimes lose track of established scientific knowledge. Their use of this kind of argument gets downright comical when they cite an alleged mystery that has, in fact, already been explained, revealing the full extent of their ignorance. For examples, see Insane Clown Posse's infamous "Miracles" video, or Bill O'Reilly's foray into oceanography.[5]

There's no reason knowledge has to come from a source that knows everything. Your parents and teachers taught you a lot, but they didn't know everything.

Science may not know everything, but its knowledge is growing; there may come a day when all the major questions have been answered by science.

Religion and other ways of knowing don't know everything either, and arguably know a great deal less than science.

That's the reason we do science in the first place: to know more than we knew before.

Science not knowing everything doesn't free you from providing evidence for your claims.

Science doesn't know everything, but it's really accurate for what it does know, and your claim would violate what science does know.

The abstract concept of science itself knows absolutely nothing - science offers an approach to finding out about things[6] rather than a sacred repository of dogma. On the other hand, humans with scientific attitudes have actually worked out a few ideas (and a few alternate ideas) that seem to explain a growing set of phenomena consistently (pending the development of better explanations).

Another way of looking at it is to consider that over centuries as we've come to understand our world better (especially, but no only, using science), naturalistic explanations have consistently replaced supernatural ones, and supernatural explanations have successfully replaced naturalistic ones exactly zero times.[7]

Creationists and anti-science people are also fond of saying "science can't explain X" when in fact there is a perfectly rational scientific explanation.[8] Or in some cases nobody has bothered to try and sort out the details, which isn't the same as saying it can't be explained.[9] Sometimes these explanations have only been arrived at recently, which makes ignorance a little more excusable but the argument no more valid.

Science can't explain how bumble bees can fly — actually they flap their wings sideways creating vortexes:[10] the calculations showing they "can't" assume they fly like airplanes, when in reality they fly like helicopters

Science can't explain the evolution of the eyeball — yes it can; the eye evolved through many steps each more useful than the last[11]

Science can't explain how an ancient civilisation created the dead straight Nazca lines — they could be done with ropes and wooden posts[8]

Science can't explain how the Pyramids were made — although we can't be sure exactly how it was done, there is no shortage of ideas,[12] and the ancient Egyptians certainly had the ability to work out the necessary mathematics to make it happen

↑"X" here may be anything for which science currently has no explanation, something for which there are several competing explanations with no consensus in the scientific community, or even robust fields of study that consistently provide reliable results, such as radiometric dating, which are then misrepresented by opponents to be riddled with error.